Keeping mixed species. opinions please! Regarding schooling necessity and predatory behaviour.

I have been given a tank of mixed species. They had lived together previously in the same tank. All good after move for 2 wks then big cat attacked black skirted tetra which died the next day followed by the diamond tetra. All others ok. 2 wks later we put four quite large mollies in and 3 of them got attacked by big cat and tin Foil barbs. We got them out and rehomed them. Put a yoyo leach in. All ok, but big cat will chase every now and then but does give up quickly. Yoyo got abrasion on back probably from dashing under the wood. Still seems ok other than that.
Question is.. should we get more cats?? Although big one.is very dominant, or more yoyo fish? I heard they can be aggressive towards own and like a hierarchy. We have 13 fish altogether.

1 boesemani rainbow ( does chase tin foils)
1 silver dollar fish ( greedy.eats all the plants but peaceful)
1 silver tetra ( peaceful)
2 clown plecos (peaceful)
1 yoyo fish (peaceful but lively)
2 different synodontis catfish, one very big ( not 100% on species, but very dominant.( smaller one hides, big one 9 inches, )
4 red tail tin foil barbs ( peaceful)
1 cherry barb ( smallest fish but never chased)

Water changed once a wk. Levels all good. Fed every other day, flakes, pellets and wafers alternate. Temp 77 .

You have very serious issues with the stocking (fish species and numbers), but before I or others deal with that, we need to know some tank data. What size tank (volume and dimensions please), and what are the source water parameters; these are GH (general or total hardness), pH and KH (carbonate hardness or Alkalinity). You should be able to find the GH and KH from your municipal water authority of you are on city water, check their website. They may show the pH too, or you may have a pH test kit (good test kit to have).

It also is important to know the Synodontis species, there are several. But it seems if you are observing aggression the 9-inch fish needs to be separated from all other fish. We need to know the species to fully figure this out...have a look at the photos on this link and see if you can find it:
https://www.planetcatfish.com/common/quick_find.php

If you click on the photo, it will open the species page which usually has several more photos to confirm.

Last, but not least, welcome to TFF.

Byron.

Tropical fishkeeper said:

Water changed once a wk. Levels all good. Fed every other day, flakes, pellets and wafers alternate. Temp 77 .

Click to expand...

Byron said:

You have very serious issues with the stocking (fish species and numbers), but before I or others deal with that, we need to know some tank data. What size tank (volume and dimensions please), and what are the source water parameters; these are GH (general or total hardness), pH and KH (carbonate hardness or Alkalinity). You should be able to find the GH and KH from your municipal water authority of you are on city water, check their website. They may show the pH too, or you may have a pH test kit (good test kit to have).

It also is important to know the Synodontis species, there are several. But it seems if you are observing aggression the 9-inch fish needs to be separated from all other fish. We need to know the species to fully figure this out...have a look at the photos on this link and see if you can find it:
https://www.planetcatfish.com/common/quick_find.php

If you click on the photo, it will open the species page which usually has several more photos to confirm.

Last, but not least, welcome to TFF.

Byron.

Click to expand...

Thank you Byron,

Tank is 5 x 2 x 2 - 566 litre
All levels are within correct range, nitrate was high a couple of weeks ago but with lots of water changes and added plants its in normal range now.
The smaller synodontis is a Synodontis Multipunctatus Catfish. The bigger one is still unknown. Picture included. He seems ok with current fish but is very dominant.
Thank you

The tank size is settled, but you did not provide us with water parameters.

On the parameters, you have fish requiring very different parameters. The Synodontis multipunctatus is a rift lake species endemic to Lake Tanganyika which has moderately hard water with a relatively high pH. This is exactly opposite to the tetras and loaches. The barbs are sort of mid-way. I'm not going to guess as to the larger Synodontis species, I am not that familiar with this genus; others may be able to help here.

Still needing the parameters, but I will move on for the moment to another issue, numbers in the individual species. Barbs, tetras and loaches are shoaling fish, living in groups of hundreds, even thousands; this need for a group is programmed into their DNA so we must provide a group in the aquarium. Minimum numbers are often suggested, but keep in mind that more will always be better for the fish, and when space permits as here, this is not a problem. But at that point we need to consider behaviours and inherent traits. Activity level of a species for example is important; except for the two tetras, you have basically active swimming fish, so that is good; active fish mixed in with sedate fish is not a good idea.

Silver Dollars are primarily vegetarian, so if you want plants to thrive, this is not a good species. So rather than acquiring a group of 6-7 of these, you might want to remove the lone SD (stores, other hobbyists).

I do not want to go too far in this without knowing the parameters. If you have moderately hard or harder water, none of these soft water species will thrive.